[PSUBS-MAILIST] Green board?

[Ian Roxborough <irox@ix.netcom.com>]

Hi,

I was wondering, is anybody considering using classic red/green check
lights board type thing to make sure all hatches and valves are closed
before diving?

It seems that this could be simple to construct; some small magnets
and some reed switches hooked up a couple of transitors and LEDs (or a
PIC/microcontrol if you want to get fancy).  Attach the magnets to the
valve handle or edge of the hatch, and place the reed switchs in a
static position (i.e. not on the handle) next to the magenets when
the valve is in the closed position, so they will be activated in
when the handle is in the closed position.

Of course this isn't full proof, the magnet might be near enough to
activate the reed switch when the hand is still slightly cracked open.
So this isn't a first line of defence, but a second check that you
didn't skip something on your check list by accident.  If you see
any reds lights after your check list has been checked, then you
need to investigate and go over your check list to make sure nothing
else was missed.

The nice thing about reed switches is that they don't create false
positives in a damp environment.  Of course the connections to the
reed switch (and any other electronics) will have to potted correct
to prevent any short circuits when/if the humity rises.

If I get some spare cycles I'll see if I can figure out the simplest
circuit for a red/green board using reed switches.  If nothing else,
it might look pretty. :-)

Cheers,
  Ian.



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